This invention relates to a parameter supply device for storing parameters determining characteristics of a tone such as waveshape data in a memory of an electronic musical instrument and reading out these parameters in accordance with plural parameter determining factors and, more particularly, to improvement in an address system for accessing the memory.
In a case where tone waveshapes of different characteristics are to be generated in accordance with plural tone color control factors (e.g., key touch, tone range or tone color selection information etc.), waveshapes of different characteristics are stored in a memory and these waveshapes are selectively read out in accordance with the tone color control factors. In a prior art device, the memory storing such waveshapes is directly accessed in accordance with the tone color control factors and, in this case, the following problem arises.
If the memory has a common construction for all combinations of control factors, there occurs waste of the memory capacity. If, for example, the adopted construction is such that waveshapes corresponding to key touch in N stages are stored for each tone range, the memory must have a capacity for storing waveshape data of N times of the number of the tone ranges. It is however unnecessary in some tone ranges to store waveshapes which are different for the respective key touches of the N stages and common waveshape data can be used for two stages or three stages in one tone range. In such case, there occurs waste in the memory construction in which N waveshape data are stored for each tone range because the same waveshape data are stored in duplication in some tone ranges.
If the memory construction is changed in accordance with the combination of the control factors, i.e., in such a case that common waveshape is stored for key touches of every two stages in some tone ranges, other common waveshape data is stored for key touches of every three stages in other tone ranges and waveshape data which is different for each stage of key touch is stored in still other tone ranges, waste of the memory capacity can be avoided. In this case, however, an address generation circuit must be constructed in such a manner that it can generate proper address signals for all combinations of the control factors which results in a very complex circuit construction. Besides, the change in the memory construction must be accompanied by change in the hardware construction of the entire address generation circuit and this involves a troublesome change in the circuit design.